Year	% of total
1970	11.435282747626005
1971	11.555450266649256
1972	13.76351953888461
1973	12.476322914840178
1974	13.059158451675348
1975	12.392622694334818
1976	11.369805475642924
1977	11.983379035671973
1978	11.571526395617752
1979	11.179070946794434
1980	13.43021550677975
1981	13.055030295831985
1982	13.01840320862549
1983	13.946001902416057
1984	15.808173134760578
1985	15.98521884192462
1986	17.789143015812805
1987	13.32270950414927
1988	14.099396692170691
1989	9.843729691221554
1990	27.982162764771463
1991	25.24807056229327
1992	22.914349276974416
1993	20.697412823397077
1994	18.080357142857142
1995	15.317286652078774
1996	13.494461228600201
1997	12.169811320754716
1998	11.081081081081082
1999	9.941027801179445
2000	10.576015108593012
2001	11.752136752136751
2002	9.562109025915996
2003	9.146341463414634
2004	8.900523560209423
2005	8.56898029134533
2006	26.863666890530556
2007	38.67403314917127
2008	45.06089309878214